login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A234098 Primes of the form (p*q + 1)/2, where p and q are distinct primes. 4
11, 17, 29, 43, 47, 67, 71, 73, 89, 101, 103, 107, 109, 127, 151, 191, 197, 223, 227, 241, 251, 269, 277, 283, 317, 349, 359, 373, 397, 409, 433, 457, 461, 467, 487, 521, 541, 569, 571, 631, 643, 647, 659, 673, 701, 709, 719, 733, 739, 751, 757, 769, 821 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

EXAMPLE

11 = (3*7 + 1)/2, 17 = (5*7 + 1)/2.

MATHEMATICA

t = Select[Range[1, 7000, 2], Map[Last, FactorInteger[#]] == Table[1, {2}] &]; Take[(t + 1)/2, 120] (* A234096 *)

v = Flatten[Position[PrimeQ[(t + 1)/2], True]] ; w = Table[t[[v[[n]]]], {n, 1, Length[v]}]  (* A233562 *)

(w + 1)/2 (* A234098 *)  (* Peter J. C. Moses, Dec 23 2013 *)

PROG

(Haskell)

a234098 n = a234098_list !! (n-1)

a234098_list = filter ((== 1) . a010051') $

                      map ((flip div 2) . (+ 1)) a046388_list

-- Reinhard Zumkeller, Jan 02 2014

CROSSREFS

Cf. A234096, A233562, A234095.

Cf. A010051, A046388.

Sequence in context: A178128 A111255 A060213 * A153502 A249377 A211486

Adjacent sequences:  A234095 A234096 A234097 * A234099 A234100 A234101

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Dec 27 2013

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 18 22:39 EST 2019. Contains 329305 sequences. (Running on oeis4.)